A broad variety of carbon blacks have been disclosed in the art. These blacks differ in many properties from each other and are made by different procedures. The main field of use of the blacks depends upon their properties. Since the carbon black as such cannot be sufficiently characterized by its chemical composition or by its ingredients, it has become widely accepted to characterize the carbon black by the properties it exhibits. Thus, the carbon black can, e.g., be characterized by its surface area which is usually an inverse measurement of the nodule size. Another important characteristic of the carbon black is its structure, which is a measure of the complexity of the individual carbon black aggregates or of the number of nodules "fused" together in one carbon black aggregate.
Great efforts have been made in the industry to correlate properties of rubbers incorporating carbon black and properties of carbon black. Unfortunately, there is not one single property of carbon black that, if made high or low enough, results in an ideal rubber composition. Certain properties of carbon black are related to abrasion of the rubber composition; others are related to the tensile strength; others are related to the heat buildup; etc.
Efforts have been made to correlate the tint or tinting strength of carbon black to the abrasion resistance of rubbers. In this connection the statement has been made that high-tint carbon black incorporated in rubber results in highly abrasion-resistant rubber compositions. As will be shown, no such correlation exists.
High abrasion resistance of a carbon black/rubber composition is one desirable property of such a composition. Another desirable property is low heat buildup or low hysteresis. The heat buildup is a measurement of how much of the elastic deformation energy put into a carbon black/rubber composition remains in this composition as heat after the deformation forces have been released. The hysteresis, or heat buildup, is measured by measuring the temperature of a sample subjected to deformations. This property, hysteresis, of carbon black/rubber compositions is very important, particularly for tires made with such a composition. The higher the heat buildup, the greater the chances are that tires made from such rubbers are destroyed or even begin to burn. Serious accidents have been attributed to the failure of tires made from such high heat buildup rubber compositions. It would, therefore, be very desirable to reduce the heat buildup of rubber/carbon black compositions.